4章-? Connections and ListsTweet
When you create GraphQL schemas, you can define fields that return lists of any GraphQL type. Lists are created by surrounding a GraphQL type with square brackets. [String] defines a list of strings and [PhotoCategory] defines a list of photo categories. As Chapter 3 discusses, lists can also consist of multiple types if we incorporate union or interface types. We discuss these types of lists in greater detail toward the end of this chapter.
Sometimes, the exclamation point can be a little tricky when defining lists. When the exclamation point comes after the closing square bracket, it means that the field itself is non-nullable. When the exclamation point comes before the closing square bracket, it means that the values contained in the list are non-nullable. Wherever you see an exclamation point, the value is required and cannot return null. Table 4-1 defines these various situations.